In recent years, ink-jet recording systems, which enable simple formation of images at low cost, have been applied to various printing fields such as photography, various printing, and special printing such as marking and color filters. Specifically, by employing ink-jet recording apparatuses which eject minute dots of ink and control them, ink-jet inks which have been improved in color reproduction, durability, and ejection adaptability, and specialized paper media which have been enhanced in color forming properties of colorants and surface glossiness, it has become possible to achieve image quality comparable to conventional silver halide photography. Image quality of the present ink-jet recording systems is enhanced only when an ink-jet recording apparatus, an ink-jet ink and a specialized paper medium are simultaneously improved.
However, ink-jet systems which require specialized kinds of paper result in problems such that recording media are limited and using such recording media increases cost. Accordingly, many trials have been made in which recording, employing the ink-jet systems, is carried out on transfer media which differ from specialized kinds of paper. Specific systems include a phase-changing ink-jet system employing a wax ink which is solid at room temperature, a solvent based ink-jet system employing rapidly drying organic solvents as a main component, and an actinic radiation curable ink-jet system in which, after recording, actinic radiation such as ultraviolet radiation (UV radiation) is exposed onto the deposited ink to result in crosslinking.
Of these, the UV radiation curable ink-jet system has received most attention in recent years, since it results in relatively low unpleasant odor, compared to a solvent based ink-jet system, exhibits rapid drying, and enables recording on non-ink absorptive recording media. Several methods employing the above UV radiation curable ink-jet ink are disclosed (refer, for example, to Patent Documents 1-5). However, when these UV radiation curable ink-jet inks are employed, the diameter of dots of each of the colors is subjected to a large change, due to the time lag from the deposition of each of the colored inks, employing different colorants, to curing, resulting in problem of the degradation of image quality.
For example, disclosed as an image quality enhancing technique is a method in which the viscosity, surface tension and photographic speed are regulated for each of the colored inks (refer, for example, to Patent Document 6). However, in particular, when the viscosity and surface tension are changed for each type of colored ink, the ejection stability of each ink differs markedly, whereby it has been not possible to stably form images.
(Patent Document 1) Japanese Patent Publication Open to Public Inspection (hereinafter referred to as JP-A) No. 6-200204
(Patent Document 2) Japanese Patent Publication Open to Public Inspection (under PCT Application) No. 2000-504778
(Patent Document 3) JP-A No. 2002-188025
(Patent Document 4) JP-A No. 2002-60463
(Patent Document 5) JP-A No. 2003-252979
(Patent Document 6) WO-03/No. 074619 Pamphlet